These bats sound very different to one another but there are bat species that sound very similar, particularly when within the same genus. Daubenton’s, Natterer’s, Whiskered and Brandt’s bats, which are usually more rural and woodland species, belong to the Myotis genus. They sound very similar and it is most often impossible to differentiate between them. This is why we need more sophisticated bat detectors and bio-acoustic software to analyse the bat calls in detail. Even then it is often impossible to determine if we have made a detection of a specific species. To be able to do this the detections need to be perfect, or nearly perfect. This is most often not the case when surveying in the field. There are many external factors that prevent the detector from receiving a perfect bat call, such as the distance and direction of the bat and background noise. Most often we may receive a detection and only be able to determine to the genus level, not individual species. In which case we would like more surveys undertaken in the same area to increase our chances of detecting better bat calls and use a more sophisticated bat detector (the SM2 – link). So not only do we require a survey undertaken in every one of the 119 km2, but we would also like complimentary surveys wherever bats are detected where we are unable to determine species and where we may have discovered high numbers of bats, in particular to try to establish if there are roost sites nearby.

Bat data

Using AnalookW software we can determine bat calls by the shapes produced on the sonogram. A sonogram is basically a graph that shows you the frequency (pitch) that a bat is vocalising at against time. The following call is from a Common Pipistrelle. They have the characteristic “hockey stick” shape.